CUDA Navier-Stokes Solver

This is the first working version of a CUDA Navier Stokes Solver I have written as a Houdini plugin.
It uses Semi-Lagrangian advection and a Jacobi iterator for pressure projection.

The current steps are:

1. Apply force
2. Velocity self-advection
3. Diffusion
4. Project Non-divergence
5. Compute no-slip boundary conditions
6. Temperature advection